Rotating electrical machines such as automotive alternators (dynamoelectric machines) (also commonly referred to as “generators”) having a stator secured within the housing of the machine and a rotor assembly that extends axially through the motor or generator are well known. The housing often includes two spaced apart frames which provide the main structural elements of the alternator. The frame closest to a pulley, which powers the alternator via a belt drive is commonly referred to as the drive end frame. The opposite frame is commonly referred to as the slip ring end frame. The two frames support between them the rotor assembly comprising a rotor shaft with a connected rotor winding. Support bearings for the rotor assembly are typically positioned “inboard” of the pulley that turns the rotor of the generator via a fan belt from the engine, the pulley also being attached to the rotor assembly. The frames are held together typically by three or four bolts which are attached axially between ears or bosses on the outside of the frames.
Each frame has a hub. The hub includes an inner core having a central axial opening (sometimes referred to as the bearing bore). The inner core axial opening provides mounting support for an outer race of a roller or ball bearing which mounts the rotor shaft to the hub. The outer race of the bearing is typically press fitted within this central opening of the core. Extending radially outward from the core is a series of hub ribs forming ventilation openings between contiguous hub ribs. The hub ribs connect the core with a rim of the hub.
Mounted on the shaft of the rotor in a position adjacent to the hub will be a fan. During operation of the alternator fan blades pass close by the hub ribs, essentially shearing the air as the blades pass near the hub ribs.
Presently, bearings that support the rotor assembly are exposed to the elements subjecting them to contamination, thus reducing the life of the bearings and the pulley. Present technology depends on one of two items for protection from contamination: the pulley or an external/outboard drive end fan.
Dual internal fan (DIF) alternators are especially susceptible to contamination of the drive end ball bearing because the ball bearing is placed in a location that is more exposed to the elements compared to prior art alternators. This is aggravated further by the large variation in customer pulleys that are often used in alternators. In particular, smaller diameter pulleys increase exposure of the drive end bearing to contamination.
Accordingly, contamination protection for the drive end bearing is desired that provides unrivalled protection with no sensitivity to the pulley used by the end-user.